Tag Archives: polyunsaturated fatty acids

In Part I of this series, we looked at the longstanding recommendations of many governmental health organizations to reduce dietary saturated fat and replace it with omega-6 fats. Doing so supposedly, these organizations claim, reduces cardiovascular disease (CVD) risk. As we saw in Part I, however, there is considerable controversy within the nutrition science community concerning this claim. There’s a case to be made for decreased saturated fat, but there’s also a case for decreased omega-6. Since the current science is far less black-and-white than the recommendations would lead you to believe, with Part II of this series, we’ll be looking at the debate from a paleolithic perspective, with the hope of gaining a broader and more balanced perspective on optimal consumption levels of both saturated and polyunsaturated fats.

Paleo PUFA Consumption

Although conclusive scientific studies are lacking, we can gain valuable insight by examining the diets of our Paleolithic ancestors. How much of these nutrients did they consume? How do current PUFA recommendations compare to PUFA consumption by our Paleolithic ancestors?

To know how much saturated fat and PUFAs they ate, we first must estimate how much total fat they ate. As always, Paleolithic diets varied based on geography and access to certain foods, but in general, our ancestors ate relatively more fat, more protein, and less carbohydrate, compared to contemporary diets. In 2000, Dr. Cordain and his colleagues estimated the following macronutrient ratios for Paleolithic diets:[1]

Fat: 28-58% of calories

Protein: 19-35% of calories

Carbohydrates: 22-40% of calories

They arrived at these estimates, in part, by analyzing the diets of 229 hunter-gather societies, assessing their specific foods, and measuring their ratios of plant to animal food consumption. The vast majority (73%) of these societies derived more than 50% of their calories from animal foods [2].

Next, we need to estimate how macronutrients are distributed within the specific foods our ancestors ate. Figures 1 and 2 below compare the meat of wild animals with the meat of commercially raised animals. Figure 1 shows the percentage of calories from protein, fat, and carbohydrate (note that carbs are negligible in animal meat) whereas Figure 2 shows each type of fat as a percentage of total fat. We can assume, with a reasonable degree of certainty, that wild animals today are similar to those hunted and consumed by our ancestors, with respect to body composition.

1. Wild meat is proportionally higher in protein and lower in fat compared to commercially raised meat.
2. The fat portion of wild meat is proportionally higher in PUFAs – both omega-6 and omega-3 – compared to commercial meat.

Additionally, we can say that grass-fed beef is closer to wild meat than grain-fed beef, but both grass-fed beef and grain-fed beef poorly approximate wild meat.

The above observations are based on data from the USDA Nutrient Database and are substantiated by numerous studies comparing wild and domesticated animals [3], [4], [5], [6], [7].

Additionally, scientists have recently extracted frozen, Paleolithic-era animal carcasses from the Siberian tundra. Tissue analyses of these carcasses further highlight the similarities between Paleolithic meat and modern wild meat, particularly with respect to n-6/n-3 ratios [8], [9].

The Ever-Important Omega Ratio

As we saw in part I, many RCTs, observational studies, and meta-analyses addressing omega-6 consumption fail to properly account for omega-3 consumption (and the n-6/n-3 ratio). For our Paleolithic ancestors, this ratio was approximately 1/1 (and probably no higher than 3/1) [10]. Today, however, the ratio approaches 20/1 for people consuming typical Western diets [11].

This disparity is critical to the entire debate about saturated fat and its replacement with omega-6. Recent studies show saturated fat isn’t a health menace, as previously believed [12][13][14][15]. On the other hand, our reliance on commercially raised meat has probably skewed our fat consumption by over-representing saturated fat and under-representing PUFAs. We’ve compensated by consuming large quantities of vegetable oils, which are rich in omega-6, but omega-3 consumption has fallen by the wayside.

The consequences of our dramatically elevated n-6/n-3 ratios include the following:[16]

Increased inflammation

Increased leptin and insulin resistance

Increased risk for diabetes

Increased weight gain and risk for obesity

Keeping it Real

Just as previous generations shunned saturated fat, we would be foolish to shun omega-6 completely. After all, omega-6 is an essential fatty acid (EFA), meaning our body requires it and can only obtain it from food. That being said, some sources of are better than others.

It’s easy to get good quality omega-6 from olive oil, avocados, nuts, and from certain animal foods. By following the Paleo Diet template, you’ll get a good balance of omega-6 and omega-3, plus a good distribution of SFAs, MUFAs, and PUFAs.

With respect to omega-6, our best advice would be to eliminate all vegetable and seed oils from your diet. These include, among others:

Soybean oil

Corn oil

Safflower oil

Sunflower oil

Canola oil

Grapeseed oil

The problem with these oils is they contain very high amounts of omega-6. Consuming them increases your n-6/n-3 ratio, while also introduces potentially dangerous free radicals.

Unstable Seed Oils

The industrial processing of vegetable seed oils involves high-heat and the use of various chemical solvents – a guaranteed recipe for free radical oxidation and lipid peroxidation [17].

Cooking with PUFA-rich oils creates lipid oxidation products known as alkenals, some of which are toxic [18].

Olive oil, which contains some PUFAs, but is mostly comprised of MUFAs, has been shown to be more heat-stable and better for cooking compared to vegetable oils [19],[20]. It’s best to avoid high-heat cooking with any oils, but those containing higher amounts of SFAs and MUFAs are more stable than those with higher amounts of PUFAs.

Conclusion

Saturated fat isn’t unhealthy, but it needn’t be over represented in our diets. Many health authorities recommend replacing saturated fat with omega-6, and although some studies support this recommendation, most fail to differentiate between omega-6 and omega-3. Replacing some saturated fat with PUFAs could be beneficial, particularly if doing so lowered the n-6/n-3 ratio. For most people, this would mean eliminating all vegetable seed oils, while increasing oily fish (omega-3) consumption.

It’s also important to recognize that meat from game animals is better than commercially raised meat, but since obtaining wild meat is impractical for most people, pasture-raised meat (grass-fed, etc.) should always be favored.

Don’t over complicate things too much. You don’t need to meticulously track your fat consumption. By following The Paleo Diet template and listening to your body, you’ll get a healthy mix.

[14] Astrup, A., et al., The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010? American Journal of Clinical Nutrition, 2011. 93(4): p. 684-688.

For over a decade now, a debate has been raging within the nutrition science community. One side views saturated fat as generally unhealthy; they recommend replacing these fats, at least to some degree, with omega-6 polyunsaturated fats. The other side views saturated fat as health-supportive, or at least health-neutral; likewise, they regard omega-6 as somewhat unhealthy and typically recommend decreasing its consumption. So, who has it right? The truth seems to be grey and somewhere in between.

The Modern Diet

Americans have largely followed the US government’s dietary advice for the past 40 years. For example, following official dietary advice in the 80s to reduce fat in our diets, we decreased our fat consumption from 45 to 34% of calories, on average, while increasing our carbohydrate consumption from 39 to 51% of calories [i].

We made these changes because doing so – or so we were told – would decrease cardiovascular disease (CVD), which was and still remains the number one cause of death in the western world.

However, there are also different types of fats (see Figure 1) and both international and US government guidelines have made recommendations about the types of fats we should consume. Current recommendations suggest reducing saturated fat to a maximum of 10% of total calories while increasing omega-6 to somewhere between five and 10% of total calories [ii], [iii].

Figure 1. The basic types of fat.

As a population, we’re pretty much within these recommended zones. We get 11% of our calories from saturated fat and 8% from polyunsaturated fat (primarily the omega-6 variety)[iv], [v].

CVD mortality has declined since its peak in the 1950s, but CVD prevalence remains very high. For example, the total number of inpatient cardiovascular operations and procedures increased 28% between 2000 and 2010 (from 5.9 million to 7.6 million procedures) [vi]. Moreover, prevalence of metabolic syndrome, a precursor to CVD, has reached a staggering 34% of the population [vii].

If the advice to replace saturated fat with omega-6 was designed to reduce CVD, then what went wrong? Was the advice misguided? Let’s look at the evidence.

The Pro-PUFA Studies

Numerous recently published meta-analyses support the conclusion that replacing saturated fat with polyunsaturated fat (though not necessarily omega-6) leads to modest CVD risk reductions. For example:

Study Limitations: PUFA consumption for this study included both omega-6 and omega-3. Therefore, it’s possible the positive results may have been primarily from omega-3; negative effects from omega-6 could have been masked.

Hooper L, et al. (2015) pooled data from 13 long-term RCTs encompassing 53,300 participants. They found “a small but potentially important reduction in cardiovascular risk when saturated fat intake was lowered,” particularly by replacing saturated fat with PUFAs, but not by replacing it with carbohydrates [ix]. However, the study found no clear effect of reducing saturated fat on total mortality.

Study Limitations: Among these RCTs, omega-6 and omega-3 PUFAs were grouped together. Therefore, analyzing the individual impact of either PUFA was not possible.

Study Limitations: (1) Whereas this study did specifically measure omega-6, it didn’t account for the ratio of omega-6 to omega-3 (referred to as “n-6/n-3” hereafter), (2) the meta-analysis only included observational studies, not RCTs, and (3) the meta-analysis measured cardiovascular disease mortality, but not all-cause mortality.

Yanping Li, et al. (2015) conducted a meta-analysis of two observational studies, the first of which followed 85,000 women for 24 years and the second of which followed 43,000 men for 30 years. In total, 7,667 cases of CHD were documented. The authors concluded that replacing 5% of the energy intake from saturated fats with equal energy from PUFAs was associated with a 25% reduced risk of CHD [xi].

Study Limitations: (1) The study was observational (no RCTs were included), (2) the study didn’t account for the n-6/n-3 ratio, and (3) the data was derived from food frequency questionnaires.

Wu JH, et al. (2015) conducted a cohort study of 2,792 older US adults (mean age, 74). To avoid the problems associated with food frequency questionnaires, they analyzed circulating omega-6 (LA only) blood levels, an objective biomarker of LA consumption[xii]. Those within the highest quintile of circulating LA had 13% lower all-cause mortality than those in the lowest quintile. Interestingly, when the authors stratified subjects based on combined LA and omega-3 PUFA concentrations, those in the highest quintile had a 54% lower all-cause mortality risk compared to those in the lowest quintile.

Study Limitations: This study was designed better than most, but didn’t completely demonstrate how changes to the n-6/n-3 ratio affect mortality.

The Anti-PUFA Studies

Christopher Ramsden, MD is a clinical investigator for the National Institutes of Health. During the past decade, Ramsden has been among the most prominent scientists challenging the mainstream narrative that omega-6 should replace saturated fat. Through a series of studies, most of which were published by the British Medical Journal, Ramsden and his colleagues have put forth an important antithesis [xiii], [xiv], [xv]. Some of their conclusions include:

Substituting dietary omega-6 LA in place of SFA increases all-cause mortality risk, as well as risks from coronary heart disease.

Benefits previously attributed to greater intake of total PUFAs may be specifically attributable to omega-3 and not to omega-6 LA.

Some of the problems with the studies used to justify increased omega-6 consumption, according to Ramsden and his colleagues, include:

Failure to distinguish between trials that selectively increased omega-6 and those that substantially increased omega-3

Failure to acknowledge that omega-6 and omega-3 replaced not only SFAs, but large amounts of trans-fats in many trials used in the pro-PUFA meta-analyses

Failure to provide the specific compositions of the diets (particularly with respect to omega-6 and trans-fat) used in the pro-PUFA meta-analyses

Failure to analyze the impact of n-6/n-3 ratios

The Middle Ground

As you can see, the consumption of saturated fat and omega-6 are controversial, partly because we lack rigorous studies specifically designed to test the optimal balance between saturated fat, omega-6, and omega-3. This was precisely the conclusion of a 2015 Cochran review by Al-Khudairy L, et. al. [xvi].

The authors sought RCT data demonstrating the effectiveness of increasing or decreasing omega-6 for the prevention of cardiovascular disease. Additionally, they wanted to assess the impact of total omega-3 consumption and the n-6/n-3 ratio.

Unfortunately, “very few trials were identified with a relatively small number of participants randomized.” They concluded, (1) there is currently insufficient evidence to recommend either increased or decreased omega-6 consumption, and (2) larger, better RCTs on this topic are needed.

Conclusion

In Part 1 of this article series, we’ve seen that many critical questions about optimal saturated- and polyunsaturated fat consumption levels haven’t yet been answered by science. While we wait for better RCTs to be conducted, we can gain deeper insights and a better understanding of this issue by examining the fat consumption patterns of our Paleo ancestors. Be sure to check out Part II of this series, where we’ll do just that.

[xi] Yanping Li, et al. (Oct 2015). Saturated Fats Compared With Unsaturated Fats and Sources of Carbohydrates in Relation to Risk of Coronary Heart Disease. Journal of the American College of Cardiology, 66(14). Retrieved from (link).

Symptoms of vitamin E deficiency are rare, but according to at least four national surveys, most Americans consume less than the government’s Recommended Daily Allowance (RDA) of this essential nutrient.1 The authors of an August 2015 study published in PLOS-One call vitamin E a “shortfall nutrient” because over 90% of Americans consume insufficient quantities and because low vitamin E status has been linked to multiple health consequences, including increased total mortality.2

Vitamin E is clearly important, but can the Paleo diet provide adequate levels? After all, some of the most frequently cited “best dietary sources” aren’t Paleo compliant. Are supplements necessary? The RDA for males and females above 14 years of age is 15 mg daily. The following table shows vitamin E values for 100 grams of various foods and their corresponding RDAs.

The foods highest in vitamin E are predominantly seeds/nuts and their oils. Seed oils are excluded from the Paleo diet, however, primarily because they contain excessive amounts of polyunsaturated fatty acids (PUFAs). Almonds, hazelnuts, and sunflower seeds are good Paleo vitamin E sources. Fruits and vegetables are also good, but they contain very low amounts. Those small amounts accumulate, however, so collectively they are indeed significant.

Probably the best Paleo vitamin E source is olive oil. One tablespoon packs 1.9 mg, which is 10% of the RDA. You can add a few tablespoons of olive oil on salads or cooked vegetables, or use it for cooking. Olive oil becomes even more attractive when you consider its relatively low levels of PUFAs.

We should note that vitamin E functions primarily as an antioxidant, which means it protects against cellular damage by scavenging for free radicals. PUFAs have a high propensity to oxidize and oxidation creates free radicals. Therefore, high levels of PUFAs can negate vitamin E’s benefits. If we refer back to our chart, we see that many foods rich in vitamin E are also PUFA-rich.

Back in 1988, Brazilian scientists theorized that total vitamin E content is not the best indicator of vitamin E activity for vegetable oils. Using high-pressure liquid chromatography, they analyzed various oils for vitamin E activity and determined that high PUFA content offsets vitamin E activity and that oil refinement causes vitamin E losses upwards of 22%, especially during steam deodorization.3 They proposed that for vitamin E, unrefined oils beat their refined counterparts and that the ratio of vitamin E to PUFA better indicates vitamin E potential compared to absolute vitamin E levels.

A British Journal of Nutrition study published this month (October 2015) reiterates the same point: “The vitamin E requirement will increase with an increase in PUFA consumption and with the degree of unsaturation of the PUFA in the diet.”4 Another just-published study is also raising interest about vitamin E, particularly for its conclusion that those who have metabolic syndrome (about one-third of the US population) don’t absorb vitamin E as effectively as those who are healthy.5 Lead author of this latter study, Richard Bruno, commented, “Dietary requirements of nutrients are generally defined only in the context of what a healthy person needs, but considering that two-thirds of Americans are overweight or obese, a healthy person might not be representative of our society. This work tells us that at least one-third of Americans have higher vitamin E requirements than healthy people.”6

With all this in mind, one might conclude that supplementation is the best way to maintain adequate vitamin E levels. In the 1980s, scientists began to understand how free radicals contribute to atherosclerosis, cancer, vision loss, and various other chronic conditions. This sparked interest in the preventative potential of antioxidant supplements, particularly vitamin E. Several observational studies, including the Nurses’ Health Study, suggested 20 – 40% reductions in heart disease risk among people taking vitamin E supplements.7

Follow-up randomized controlled trials, however, dampened enthusiasm for vitamin E supplements, both for heart disease and cancer prevention. One meta-analysis even concluded that high-dose vitamin E supplementation may increase all-cause mortality and should be avoided.8 For those who are interested, the Harvard School of Public Health has an excellent summary on the history of research on vitamin E supplementation.

In conclusion, supplementation may provide benefits for certain conditions, but food sources of vitamin E are widely considered to be superior. Many of the richest food sources, however, are high-PUFA seed oils. High levels of PUFAs counteract vitamin E’s antioxidant capacity. It’s best to eliminate vegetable seed oils from your diet. The Paleo Diet provides plenty of vitamin E via olive oil, small quantities of seeds and nuts, and large amounts of vegetables.

There has been extensive debate within the Paleo community recently surrounding the validity of certain cooking oils while following The Paleo Diet.

Hunter-gatherers would have not had access to most cooking oils available to modern society. That being said, animal fats were likely consumed and used as a substitute for cooking oils that are commonly consumed today. Grilling eliminates the need for cooking with oil in pans, but grilling food for every meal is not very realistic for the average individual following a contemporary Paleo Diet.

However, there are a number of common cooking oils that should never be consumed while following The Paleo Diet. These include:

Soybean Oil: Often partially hydrogenated and is highly inflammatory due to the disproportionately high ratio of omega-6 to omega-3 fatty acids.

Canola Oil: Derived from the unpalatable rapeseed plant, the oil is stripped of erucic acid to make it edible. Canola oil is often praised for its omega-3 content, but health practitioners often fail to account for the quick degradation of omega-3 fatty acids within the oil due to the 500 degree temperature that is required to manufacture the oil.

Cottonseed Oil: Derived from an inedible plant that is used in the textile industry, the oil is used in numerous processed foods including margarine, ice cream, bread, and packaged oysters. As with Canola, Cottonseed also has an unhealthy fatty acid profile and should be avoided at all costs.

Other cooking oils to avoid for rancidity, inflammatory properties, and an unbalanced fatty acid profile:

Safflower Oil

Sunflower Seed Oil

Sesame Seed Oil

Peanut Oil

Corn Oil

Vegetable OilGrape Seed Oil

Despite the overwhelming majority of unhealthy oils that are available for purchase at your average grocery store, there is still hope! Swap out the bad for the oils permitted when following The Paleo Diet.

Olive Oil: Fantastic for sauteing and as a salad dressing. It is fairly resistant to high heat, which makes it less prone to rancidity. It primarily consists of monounsaturated fats, which are considered safe and healthy.

Coconut Oil: While the tropical, shelf-stable oil is relatively high in saturated fats, the saturated fat content should not be a concern and allows for the oil to remain stable at high temperatures. Coconut oil is also very rich in a medium chain fatty acid known as Lauric Acid, which is recognized for its antimicrobial and antifungal properties.

Animal Fat: Realistically, this is the closest to a hunter-gatherer cooking fat or oil. Grass-fed beef tallow is preferred. Duck fat is also allowed. However, be careful when consuming fat from pork or chicken, as both contain significantly higher quantities of polyunsaturated fats.

Although there are numerous toxic and potentially lethal species of mushroom species, you should not be worried about consuming the mushrooms you find at your choice grocer. In all likelihood, our hunter-gatherer ancestors likely indulged in various types of mushrooms on a semi-regular basis, knowing the distinct properties to exclude poisonous species. Mushrooms are also relatively low on the glycemic index and are rich in selenium, potassium, riboflavin, niacin – all optimal for your health. Let the mushroom hunting adventures ensue!

Kyle Cordain
The Paleo Diet Team

Mushroom Sauté

3 – 4 Servings

Ingredients

2 cups fresh mushrooms, sliced thin

½ sweet onion, sliced thin

2 fresh garlic cloves, pressed

2 tbsp extra virgin olive oil

¼ cup red wine

2 leaves fresh basil finely chopped

1 sprig fresh rosemary, minced, stem removed

Grass-Fed Beef or Buffalo Steaks

Directions

1. In large fry pan, saute onions and garlic in olive oil over medium heat until onions are tender.

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